In many known examples of automatic washing apparatuses, particularly dishwashing machines, it is commonly necessary for one or more selected washing materials, e.g. detergent, water softener, rinse aid, to be delivered to the interior of the apparatus for dispersion into the wash liquor at a particular point or stage in the washing cycle which is not at its beginning. With the prevalence of automatic washing machines which conduct the washing cycle without the need or even ability for human intervention during its progress, it has therefore been necessary to find ways of introducing the required washing material(s) in such a way as to optimise their action, minimise waste and preferably deliver them only at the point or stage in the cycle at which they are needed.
One way in which this aim has hitherto been achieved is to incorporate in the machine specially controlled delivery means which enable a dose of the required washing material to be charged into the machine before the cycle commences and retained in a closed compartment until the predetermined point or stage in the cycle is reached, at which time the delivery means are triggered to release the dose of washing material into the interior of the machine at exactly the desired predetermined time in the cycle. The delivery means is triggered to release the dose of washing material by the wash cycle timing control system.
In a practical example of this known delivery system in a machine dishwasher, a compartment is provided on the inside of the door of the machine, into which compartment a dose of usually dishwashing detergent is loaded prior to the wash cycle commencing. The compartment is closed by a retractable door or cover to keep the detergent shielded from water within the machine until such time as delivery of the detergent is triggered by the machine control system at the appropriate predetermined point in the cycle. At that time the compartment door or cover is retracted to allow water to reach and flush out the detergent into the interior of the machine. In a typical dishwasher release of the detergent is triggered at the beginning of the main wash stage, following an initial prewash stage which may last typically for between 2 and perhaps 15 or 20 minutes.
Automatic delivery means controlled by the machine's overall control system, such as described above, do have the advantage of providing the desired degree of control over exactly when in the wash cycle a given dose of washing material is delivered, but this is not without the cost of various drawbacks.
For instance, because the triggering of the delivery means to release the dose of material charged therein is dependent upon the characteristics and duration of any preliminary stages of the wash cycle before the point or stage at which delivery of the washing material is actually required, the overall control system of the machine has to be particularly complex, especially so if the machine is designed to have considerable flexibility in the programming of various selectable combinations or series of individual stages in the overall wash cycle. This makes the complexity and cost of the control system high if the machine is designed to have a wide range of different wash programmes. Also, because the means by which opening of the compartment is triggered is an integral part of what is nowadays a completely automatic electronic control system, any malfunction thereof is correspondingly difficult to diagnose and furthermore difficult and costly to rectify.
A further drawback, following on from the above, is that since the triggered release of the washing material is controlled as an integral feature of the machine's overall control system as constructed and fitted by the machine manufacturer, this can lead to limitations on the versatility of the machine as applied to new detergent and other washing products which may be designed for new styles of use or dispensing or washing regimes. This may represent a hindrance to the development of new commercially viable washing products, particularly since nowadays dishwashing and other washing machines may remain in service for a period of many years.
From the consumer's point of view, dishwashing machines which are cheaper to buy and more straightforward to use are of course more attractive and this may lead to trends away from more technologically advanced designs of machines. This places greater pressures on designers and manufacturers to design operating and washing material release systems which offer the consumer convenience in the use and operating of machines whilst as far as possible not compromising on wash performance. Even with dishwashers for instance which do incorporate controlled release devices for detergent, and particularly in recent years since the launch of detergent in the form of tablets as opposed to the more conventional powders, it has become apparent that consumers increasingly make a habit of not using the machine's controlled release system in the way for which it was designed, but may typically drop the detergent tablet directly into the interior of the machine, e.g. into the cutlery basket, at the time the wash cycle is commenced, even though it will begin with a prewash stage before the main wash stage. Having recognised this trend, certain manufacturers have taken to supplying a simple plastic basket for accommodating the detergent tablet and which is designed to be attached to the cutlery basket or plate rack. Since the detergent is required primarily for the higher temperature main wash stage of the cycle, it is inevitable that during the prewash stage, which can last typically from anything between 2 and 15 to 20 minutes, when used in this way the detergent tablet will at best be partially dissolved during the prewash stage, thereby leaving less detergent available for delivery during the main wash stage. Certain manufacturers have reacted to this by making detergent tablets larger or by formulating the composition so that the tablet dissolves more slowly, but neither of these attempts at solving the problem are without further consequential drawbacks, since of course the first leads to increased cost and wastage, and the second leads to compromised wash performance during the main wash stage of the wash cycle, which is where release of the detergent is primarily needed.
What all these considerations have led to, therefore, is recognition by us of a need for a means of dispensing a dose of washing material into the interior of a dishwashing machine at a selected point or stage in the wash cycle which is independent of the overall machine's control system, yet is reliable in operation, is relatively cheap in design and construction, simple to use and is not at the cost of compromised wash performance. We have addressed the problem in particular in the context of delivering washing material, in particular detergent, into the interior of an automatic dishwashing machine, but the present invention which has resulted is not limited to this and may have utility in the delivery of various washing materials in various types of washing machine.